Pits on a sub-micron scale for recording signals are formed on optical discs, such as CD's or DVD's. Therefore, the surface of a substrate for a stamper requires an extremely high degree of flatness. In order to satisfy this requirement, conventionally, a nickel film is grown on the surface of a glass substrate that has been mirror polished in accordance with an electroforming method, and thereby, a substrate for a stamper having a high degree of flatness is prepared.
However, the thickness of a substrate for a stamper is, in general, approximately 300 μm. Accordingly, in accordance with an electroforming method where a nickel film is grown in order to prepare a substrate for a stamper made of nickel, the electric power consumption for growing the nickel film to the thickness of approximately 300 μm, which is the thickness of the substrate for a stamper, becomes too large, and thus, this method is not preferable, from the point of view of the cost for preparation. In addition, waste liquid is created through plating, which is not desirable, from the point of view of an increase in the cost for processing of the waste liquid and protection of the environment.
Therefore, a method for preparing a substrate for a stamper where a metal plate, for example, a rolled plate, that has been prepared through rolling from nickel or a nickel alloy (hereinafter referred to as Ni rolled plate) is cut to a predetermined size, which is then polished, has been proposed, in order to reduce the cost for preparation.
Patent Document 1 discloses, for example, a preparing method for a substrate for a stamper where an Ni rolled plate is used as the substrate for a stamper, and a chemical and mechanical polishing process is operated on the surface. In addition, Patent Document 2 discloses a method for preparing a substrate for a stamper where a chemical and mechanical polishing process is operated on a metal material that has been punched out from a hoop in coil form.    Patent Document 1: Japanese Patent Application Laid-Open No. 2002-355749    Patent Document 2: Japanese Patent Application Laid-Open No. 2001-283475